[Libav-user] "Circular buffer overrun" error when reading UDP stream

[Alex Cohn]

On Sun, Jul 28, 2013 at 5:57 PM, Adi Shavit <adishavit at gmail.com> wrote:
> Hi,
>
>   I'm decoding a UDP stream and getting "Circular buffer overrun. To
> avoid, increase fifo_size URL option. To survive in such case, use
> overrun_nonfatal option".
> How exactly do I :
>
> 1. "increase fifo_size URL option. "
> 2. "use overrun_nonfatal option".
>
> I couldn't find this is the docs.
> Thanks,
> Adi

See http://ffmpeg.gusari.org/viewtopic.php?f=12&t=624. For ffmpeg
command line, you can specify the UDP buffer size in the URL, e.g.
udp://localhost:5002?fifo_size=1000000.

Buy if you get this message because you followed my advice about max
15 FPS, you are doing something wrong on your side: you should pull
the buffers faster. Did you add a sleep in the decoder loop? If your
client is at 100% CPU utilization,  faster settings for h264 decoder
may help.

The only "legitimate" case when increase of the fifo size may really
be the correct solution, is a slow, unreliable network. In such case,
UDP packets may arrive significantly out of order, and nothing but
fifo size will compensate that.

Note that overrun_nonfatal will break the video output. If the network
is very bad, and you have IDR frames sent often enough, or if you use
an intra-refresh stream.

BR,
Alex Cohn